An optical coherence tomography (OCT) apparatus has been used for a diagnosis of arterioscleosis, for a diagnosis before operation at the time of an endovascular treatment by a high functional catheter such as a balloon catheter, a stent and the like, or for confirming results after an operation.
The optical coherence tomography apparatus is an apparatus having at its distal end an optical probe unit which is built-in with a transmitting and receiving unit mounted with an optical lens and an optical mirror, and an optical fiber inside the blood vessel. The probe is insertable into a blood vessel whereby measurement light is emitted to the blood vessel while rotating the transmitting and receiving unit. A radial scan is carried out by receiving reflected light from a biological tissue, and a cross-sectional image of the blood vessel based on interference signal is visualized by making the reflected light obtained depending on this radial scan and a reference light split from the measurement light beforehand interfere each other. An example of this optical coherence tomography apparatus is disclosed in Japanese Unexamined Patent Publication No. 2001-79007.
Recently, as an enhancement of the optical coherent tomography apparatus, an optical frequency domain imaging (OFDI) apparatus has been developed which utilizes wavelength swept light source.
With respect to the optical frequency domain imaging (OFDI) apparatus utilizing wavelength swept light source, the basic construction of the apparatus is similar to that of the optical coherence tomography (OCT) apparatus, but one difference is that a light source having a longer wavelength compared with the optical coherent tomography apparatus is used and also, light having different wavelengths is emitted continuously. Then, mechanism for variably changing the optical path length of the reference light is made unnecessary by employing a construction in which reflected-light intensity at each point in the depth direction of the biological tissue is determined by frequency analysis of the interference signal.
The description which follows refers to “imaging apparatus” which is intended to be a generic term that includes both the optical coherence tomography (OCT) apparatus and the optical frequency domain imaging (OFDI) apparatus utilizing wavelength swept light source.
Generally, on an occasion when carrying out a radial operation of a transmitting and receiving unit in order to visualize a cross-sectional image by using such an imaging apparatus, it is desirable to be minimally invasive with respect to a patient.
On the other hand, during the radial operation of the transmitting and receiving unit, occurrence of various kinds of troubles in an optical probe unit can occur such that an injury is exerted to a blood vessel of a patient. For example, in a case in which the catheter is bent extremely or in a case in which it is trapped by a stent or the like, rotation torque for rotating the transmitting and receiving unit cannot be transmitted to the transmitting and receiving unit and it takes on a state in which the optical fiber will coil on itself at the proximal side. In this case, a pulling force is added to the catheter and it happens that the catheter is damaged or bent inside the blood vessel, so that there is a possibility that injury is exerted with respect to the blood vessel.
Also, in case of carrying out pull-back in a state in which the transmitting and receiving unit and the catheter are stacked at the bent portion, at the stent or the like, similarly, a pulling force is added with respect to the catheter, it happens that the catheter can be damaged or bent inside the blood vessel, so that there is a possibility that injury is exerted with respect to the blood vessel.